Field of the Invention
The present invention relates to a controller of a variable stiffness mechanism having a dielectric elastomer, which elastically deforms according to a voltage applied thereto.
Description of the Related Art
A dielectric elastomer has the property that, when a voltage is applied thereto, the dielectric elastomer is compressed by Maxwell stresses in the direction of an electric field attributable to the applied voltage. Further, the stiffness or the like of the dielectric elastomer can be controlled to a required target state by variably manipulating the voltage applied to the dielectric elastomer (hereinafter may be referred to simply as “the elastomer”). For this reason, the elastomer has been used in a variety of technical fields in recent years.
For example, Japanese Patent Application Laid-Open No. 2003-174205 (hereinafter referred to as “Patent Document 1”) proposes a device capable of changing the stiffness of a sheet-like elastomer installed between two members, which are mutually relatively displaceable, by manipulating a voltage applied to the elastomer.
The elastomer is generally composed of a polymer (polymeric material). In this case, if a state in which an external force acts on the elastomer continues, then the creep phenomenon causes the strain of the elastomer to increase and eventually break the elastomer.
Hence, a technique for suppressing an increase in the strain of the elastomer attributable to the creep phenomenon is desired for a device like the one described in Patent Document 1.